--fgrep doesnt work with --watch

[VictorioBerra]

Expected

when using --fgrep "my search string" --watch one would think a file change would run tests with the provided fgrep string.

Actual

all tests re-run when a file is changed as if --fgrep was never used.

[fahrradflucht]

Confirmed! The fgrep flag is only recognised for the first test run. re-runs just run all tests. This is a major issue on large codebases.

[stale]

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[boneskull]

grep and watch don't play nice together.

[Janpot]

--watch + --grep used to work well for me. It just broke completely in mocha@6 for me. It just runs 0 tests.

[Janpot]

To reproduce:
given the following test file:

// ./test/index.spec.js
it('test1', () => {});
it('test2', () => {});

Running under v5:

$ npx mocha@5 --watch --grep test1
npx: installed 24 in 2.949s



  ✓ test1

  1 passing (6ms)

Running under v6:

$ npx mocha@6 --watch --grep test1
npx: installed 230 in 6.878s



  0 passing (1ms)

Without --watch:

s$ npx mocha@6 --grep test1
npx: installed 230 in 5.609s


  ✓ test1

  1 passing (3ms)

[plroebuck]

@Janpot, --watch was broken in the 6.0 release, but has already been fixed in #3755.
You can patch your version of Mocha locally in the meantime by making the same one-line change.